Diagnosis and treatment of anterior knee painVicente Sanchis-Alfonso,1 Jenny McConnell,2 Joan Carles Monllau,3 John P Fulkerson4

1Department of OrthopaedicSurgery, Hospital Arnau deVilanova and Hospital 9 deOctubre, Valencia, Spain2McConnell PhysiotherapyGroup, Centre for SportsMedicine Research andEducation, University ofMelbourne, Melbourne,Victoria, Australia3Department of OrthopaedicSurgery and Traumatology,Hospital del Mar, UniversitatAutònoma de Barcelona,Barcelona, Spain4Department of OrthopaedicSurgery, Orthopedic Associatesof Hartford; University ofConnecticut Medical School,Farmington, Connecticut, USA

Correspondence toDr Vicente Sanchis-Alfonso,Department of OrthopaedicSurgery, Hospital Arnau deVilanova and Hospital 9 deOctubre, Avd CardenalBenlloch 36, 23, Valencia46021, Spain; vicente.sanchis.alfonso@gmail.com

Received 30 December 2015Revised 23 February 2016Accepted 2 March 2016

To cite: Sanchis-Alfonso V,McConnell J, Monllau JC,et al. JISAKOS PublishedOnline First: [please includeDay Month Year]doi:10.1136/jisakos-2015-000033

ABSTRACTAnterior knee pain (AKP) is one of the most frequentreasons for adolescents and young adults to seekconsultation for knee conditions. Owing to the complexmultifactorial aetiology of AKP, with local, proximal anddistal factors potentially involved, its treatment isparticularly difficult and challenging for the practitioner.A careful history and physical examination are crucial foran accurate diagnosis and therefore a correct treatment.The entire lower extremity should be examined, withfindings complemented by imaging studies to arrive at adiagnosis. Arriving at a precise diagnosis is thecornerstone of developing an appropriate treatment.Given that the aetiology of AKP is multifactorial,individualised treatment must be tailored to the patient.Early intervention is very important to maximise thechance of a good prognosis. Non-surgical managementis effective in the majority of patients. Surgery isindicated solely in cases with pain that is refractory tonon-operative treatment and well-defined structuralabnormalities that are deemed to be the cause of theAKP can be targeted for repair or correction.

BACKGROUND, PREVALENCE, AND SOCIETALIMPACTAnterior knee pain (AKP) is one of the most fre-quent reasons for consultation in the context ofknee conditions in adolescent and young adultpatients, accounting for up to 74% of knee painexperienced by adolescents participating in sports.1

Nejati et al2 found the prevalence rate of AKP tobe 16.7% in a study performed in a sports medi-cine clinic. This rate was similar to that shown byBoling et al3 in a study that involved participantsfrom the US Naval Academy. Boling et al3 found aprevalence of 15% in females and 12% in males.They also observed that the annual incidence ofAKP was 33 of 1000 people in female patients, butonly 15 of 1000 people in male patients. Gender isa significant predictor for the development of AKP,with females having an incidence that is 2.23 timeshigher than that of males.3 However, the incidenceof AKP in the general population is unknown.Treating patients with AKP is often frustrating,

both for the orthopaedic surgeon and for thephysiotherapist. Collins et al4 have shown 40% ofunfavourable recovery at 12 months after the initialdiagnosis. Moreover, between 70% and 90% ofindividuals with AKP have recurrent or chronicpain.5 Chronic pain is a multidimensional experi-ence that requires consideration of sensory featuresas well as affective and cognitive features.6 That isto say, chronic pain affects a patient psychologically.AKP provokes both psychological limitations anddisability, which may arise more from the psycho-logical affectation than from the pain itself.7 TheWHO defines disability as ‘a limitation of function

that compromises an individual’s ability to performan activity within the range considered normal’.Such limitations may impose a change in a patient’slifestyle. Since AKP frequently occurs in youngworking adults, it has an important societal impactdue to work absences and lost productivity as wellas the economic expense involving in treating thesepatients.8 AKP is frequently met with a lack ofunderstanding within a patient’s circle of acquaint-ance, which worsens the psychological affectation.Moreover, patients with AKP may also have anincreased risk of developing patellofemoral osteo-arthritis (PFOA).9 In summary, AKP has a negativeimpact on patients’ quality of life. As an indicatorof the importance of this clinical entity, theChartered Society of Physiotherapy in the UK hasranked AKP as the third most important topic outof 185 listed in their Musculoskeletal ResearchPriority Project.10

The goal of this paper is to analyse in detail howto better reach a diagnosis and therefore identifythe most suitable treatment in individual cases. Weemphasise that the aetiology of AKP is multifactor-ial, involving local, proximal and distal factors,which leads to there being many subsets of patientswith AKP. Hence, there is no single treatment.Treatment has to be tailored to the individualpatient. In box 1, we outline 10 articles that theauthors of this paper found to be key in the devel-opment of evaluation and treatment of AKP.

DIAGNOSISThe patient’s clinical history and physical examin-ation are of paramount importance in diagnosingthe cause of AKP. The physical examination is com-plemented by imaging studies, and the combinationshould yield a precise diagnosis that will be thecornerstone in developing an appropriate thera-peutic programme. It must be emphasised that thecause of AKP should be a diagnosis of exclusion.

HistoryFirst, a complete history of the patient’s symptomsis required to diagnose. We must listen to thepatient carefully. In any pathological entity, listen-ing to the patient is essential, but in the one wedeal with in this paper, it is even more important.The main symptom experienced by a patient with

AKP is retropatellar or peripatellar pain. The loca-tion of the pain is crucial for making a diagnosis.However, it is often difficult for a patient to isolatethe focus of pain. In response to a query about thepain’s location, he or she may simply put a handover the anterior aspect of the knee. The pain mayeven be popliteal. Pain diagrams, on which patientsindicate the site of pain on drawings of the knee,could be helpful. It is also important to determinewhether the pain appears, or is aggravated by

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activities that load the patellofemoral joint (PFJ), such as climb-ing and descending the stairs, squatting, using a car clutch (if theleft knee is in pain), wearing high-heeled shoes, and sitting withprolonged knee flexion (-movie sign-), and whether extendingthe knee improves the pain.

Aside from pain, other symptoms are a giving-way sensation—walking straight on, especially when using the stairs or ramps,and crepitus. The giving-way episodes are due to a suddenreflex inhibition and/or atrophy of the quadriceps. It is import-ant to establish if patellar instability is associated with the painsince both the treatment and the prognosis are very different inthe patient with AKP secondary to patellar instability comparedwith the patient with AKP without patellar instability. Crepitusis common, although it is insignificant in most cases. Forexample, Abernethy et al21 found asymptomatic crepitus in62% of first-year medical students.

AKP onset is generally insidious and without trauma, whichreflects an overuse condition or an underlying malalignment.Overuse can be brought on by a new activity or an increase infrequency or intensity of a customary activity. History should begeared towards determining which supraphysiological loading

activity is of importance in the origin of AKP. The identificationand careful management of the activities associated with theonset and endurance of AKP are key elements for successfultreatment.18 Symptoms in both knees are common and maymove from one knee to the other over time.

AKP is often described as dull with intermittent episodes ofsharp acute pain. In obtaining the history, it is important toquantify the pain. Pain is sometimes disproportionate due toexisting hyperalgesia (heightened reaction to stimuli, ie, nor-mally painful) or allodynia (pain due to stimuli that do notusually bring on pain).22 These patients belong to the AKPsubset of neuropathic pain. Finally, in cases preceded by realign-ment surgery in which pain and disability are much worse thanthe preoperative symptoms that prompted surgery, there shouldbe suspicion of an iatrogenic medial patellar instability (IMPI).23

In addition to pain, which is the fundamental symptom, thesepatients experience disability to a greater or lesser degree.Therefore, it is also important to quantify the disability.

Patients with AKP very often experience anxiety, depression,kinesiophobia (the fear that a manoeuvre will cause more injuryor a reinjury and pain) and catastrophising (the belief that painwill worsen and cannot be relieved).7 These psychologicalfactors play an important role as pain modulators. Even if thestructural findings are clear, psychological factors influence andmodify pain sensation as well as subsequent impairment and canserve as barriers to recovery.20 Therefore, it is essential to recog-nise and quantify the existence of these psychological issues tohave a holistic view of a particular patient and plan the besttreatment (box 2).

Physical examinationThe first objective of physical examination is to pinpoint thepainful area, and to replicate the symptoms. The location of the

Box 2 Outcome measures

▸ Using tools such as the Visual Analogue Scale (VAS) of painis important in order to quantify the pain at baseline and todemonstrate and monitor improvement with the treatment.The 10 cm VAS is a valid and responsive outcome measurefor anterior knee pain, with a minimum clinically importantdifference of 2 cm.24

▸ If the presence of neuropathic pain is suspected, validatedself-administered scales that are specific for neuropathicpain, such as the Leeds Assessment of NeuropathicSymptoms and Signs (LANSS) Pain Scale, should be used.25

▸ Algometry may help clinicians in recognising patients withcomplex regional pain syndrome (CRPS). If surgeons areaware of the extent of the CRPS preoperatively, they wouldbe very cautious to not operate as the symptoms will onlyworsen.

▸ The disability may be quantified by using specific validatedfunctional self-administered scales such as the Kujala test26

and the Tegner activity scale.27 It is also necessary to knowa patient’s activity level prior to the treatment and his/herobjectives in order to review realistic goals of the treatment.

▸ We should routinely incorporate validated self-administeredscreening tests for anxiety and depression—Hospital Anxietyand Depression Scale (HADS),28 catastrophising—PainCatastrophizing Scale (PCS),29 and kinesiophobia—TampaScale for Kinesiophobia (TSK)30 in a patient’s history.

Box 1 Key articles (historic evolution), according to theauthors, on anterior knee pain (AKP)

▸ Merchant et al11 in 1974 described in depth theroentgenographic analysis of patellofemoral congruence.

▸ Fulkerson12 described in 1983 the anteromedialisation of thetibial tuberosity.

▸ In 1985, Fulkerson et al13 was the first to describe nervedamage in the lateral retinaculum of patients with intractablepatellofemoral pain requiring lateral retinacular release orrealignment of the patellofemoral joint. He stated that it islikely that the lateral retinaculum itself is painful in manypatients with patellofemoral malalignment.

▸ Hughston and Deese14 described, for the first time in 1988,medial patellar instability as a complication of lateralretinacular release that provokes incapacitating AKP.

▸ McConnell15 was the first, in 1996, to propose the use oftape to exert a force on the patella to improve alignment andtracking, this way AKP is diminished.

▸ Sanchis-Alfonso et al,16 in 1998, performed a quantitativeanalysis of nerve changes in the lateral retinaculum inpatients with AKP.

▸ Powers,17 in 2003, introduced one of the most importantconcepts of the past 13 years in AKP aetiology: the proximalcontrol. This new philosophy links abnormal femur rotationwith AKP. The rotation of the femur underneath the patella inthe transverse plane leads to abnormal patellar tracking andtherefore patellofemoral imbalance and finally pain. This meansthat the primary problem is not in the patella but in the femur.

▸ Dye18 popularised in 2005 the tissue homeostasis perspectiveto evaluate and treat patients with AKP. According to Dye,the loss of both osseous and soft tissue homeostasis is moreimportant in the genesis of AKP than structuralcharacteristics.

▸ Näslund et al,19 in 2007, demonstrated the importance ofischaemia in the genesis of pain in a subset of patients with AKP

▸ Domenech and Sanchis-Alfonso7 20 performed in 2013 and2014 the most detailed analysis of psychological factorsacting as pain modulators in AKP.

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pain is crucial because it is able to indicate the injured structure,which is really helpful in diagnosing and planning treatment.Tenderness over the lateral retinaculum is a frequent finding.Therefore, we must evaluate lateral retinaculum tightness usingthe patellar glide test.31 In order to exclude the possibility thatAKP originates in the patellofemoral articular surfaces, theaxial patellar compression test is used.31 Moreover, thesustained knee flexion test allows one to rule out painbrought on by an increase in intraosseous patellar pressure.32

Palpation of the inferior pole of the patella must beperformed in all cases because pain is very frequently located inthat area.31 Moreover, Hoffa’s fat pad should not be overlookedas a cause of pain; it should always be examined while perform-ing Hoffa’s test because it can be a source of disabling pain(figure 1).33 Existing scars should be palpated and Tinel’s signcarried out to detect neuromas. Improvement in the patient’spain after selective injection with local anaesthetics or withunloading functional taping leads us to think that specific kneesoft tissue may be the origin of pain. When a neuropathic originof pain is suspected, pressure algometry, which provides a meas-urement of pressure pain threshold by applying progressive pres-sure to a given body point using an algometer, is helpful.Female adolescents with AKP have been demonstrated to have alower pressure pain threshold in comparison with a controlgroup.22

Most patients with AKP will develop a quadriceps avoidancegait pattern to decrease the PFJ reaction force and thereby thepain.31 Notably, a knee extension strength deficit appears to bea predictor of AKP.34 Hence, it is mandatory to evaluate quadri-ceps atrophy and isometric strength of the quadriceps, whichcan be done with a manual dynamometer.

Moreover, it is necessary to evaluate the flexibility in thequadriceps, hamstring, gastrocnemius muscles, the iliotibialband (ITB) and anterior hip structures (figure 2), given that

AKP is frequently associated with a reduced flexibility of thesestructures.31

Baker et al35 showed abnormal knee joint proprioception inthose with AKP. Although they could not determine if theabnormality preceded AKP or was secondary to it, their resultssupport the inclusion of specific proprioceptive training in treat-ment. The active or passive joint position reproduction can beused to evaluate proprioception.

Normally, when a patient with AKP is seen in a clinic, thefocus is on the knee and only that structure is studied. Thisfocus is a mistake, because other important aetiological factorsdistant from the knee can be responsible for the pain.36 Strongevidence currently exists that patients with AKP have deficits inhip abduction, hip extension and external rotation strength.37

Therefore, it is mandatory in the clinical examination to evalu-ate hip abduction strength, hip extension strength and hip exter-nal rotation isometric strength, which can be done with amanual dynamometer. Moreover, a patient with AKP may havecore muscle weakness, so it is also important to evaluate thecore muscle endurance.38 Both core and hip weaknesses lead todynamic malalignment of the lower extremity that influencespatellar tracking. Tibial and femoral rotation should also beevaluated because of their influence on the patellofemoralcontact area and pressure39 (figures 3 and 4). Although lowerextremity rotational deformities might increase the risk of AKP,these deformities alone are not enough to provoke AKP; theyare only predisposing factors.40 AKP is correlated with lateral-isation of the tibial tubercle (figure 5).41 When the knee isflexed 90°, the tubercle sulcus angle should be 0°.42

Currently, evaluation of the PFJ tends to be done under con-ditions that simulate realistic functional demands using specificfunctional tasks rather than specific tests of the patella.43 Ourpreferred activity to evaluate patients with AKP is descendingthe stairs because it is the most demanding of all the activities of

Figure 1 In patients with impingement of the Hoffa fat pad, pain is dramatically exacerbated by quadriceps contraction (B) or passive kneeextension (C), while applying pressure of the fat pad with the fingers (A,B,C), because this movement causes a small posterior tilt of the inferiorpole of the patella, which impinges on an inflamed and sensitised infrapatellar fat pad.

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daily living (ADL) with regard to the knees since it requires sub-stantial control in the quadriceps contraction eccentric phase.Therefore, we perform the step-down task.17 The patient stepsdown slowly from a step. In this task, the limb going down onlybrushes the floor with the heel and then goes back to full kneeextension. Moreover, we perform the one-legged squat task(figure 6) and the landing from a drop task.17 During thesetasks, many patients with AKP have an excessive functional kneevalgus.17

Feet examination is crucial because pronated feet have animportant role in the genesis of AKP.31 Lastly, functional halluxlimitus cannot be forgotten as a potential predisposing factorfor AKP.44 It can be demonstrated by a loss of dorsal flexion ofthe first metatarsophalangeal joint with the ankle in dorsalflexion.44

Finally, if an IMPI is suspected, the Fulkerson relocation testis useful.45 To perform this test, the patella is held medially inextension and then released on abrupt knee flexion. It is a pro-vocative test, and therefore reproduction of symptomatologywith this manoeuvre strongly suggests medial patellar instability.

ImagingAKP is basically a clinical diagnosis, with imaging only assistingto complete the diagnosis. Imaging studies are aimed at quanti-fying the pathology and checking for other pathologies thatcould simulate femoropatellar pathology.

The standing anteroposterior view, a true lateral view, andaxial X-rays should be obtained for all patients with AKP.These X-rays are the first steps for imaging. In cases refractoryto conservative treatment, CT and MRI should be considered.CT shows the bone morphology and allows the measurement ofimportant knee parameters, such as the tibial tubercle-trochlear

Figure 2 Assessment of the flexibility of the anterior hip structures.

Figure 3 Both internal femoral rotation and external tibial rotation increase pressure on the lateral side of the patellofemoral joint.39 Squintingpatella when the patient is standing with their feet forward. It is due mainly to femoral anteversion, but it can be seen in cases with external tibialtorsion without femoral anteversion as occurs in this particular case. Examination of the hips demonstrates equal internal and external rotation. Inpatients with an increment of the femoral anteversion, the internal rotation of the hip is greater than the external rotation. We must note thatincreased foot pronation can also lead to increased internal tibial rotation and thus ‘squinting patellae’.

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groove distance (TT-TG), that allow for evaluation of maltrack-ing. Moreover, CT scans can detect and quantify torsionalanomalies of the lower limbs (figure 4). MRI is useful for detec-tion of cartilage lesions in the PFJ, intraosseous oedema, syn-ovial plica and soft tissue impingement (figure 7). Imaging

findings such as lateral patellar displacement may be frequentlyseen in asymptomatic patients.31 Patellofemoral chondropathy isalso extremely common, and only a small number of patientswith a patellar chondral lesion have AKP related to it.Therefore, a surgical option ought never to be based only onimaging techniques, as the correlation between clinical findingsand imaging is not good. Three-dimensional CT could be clinic-ally useful in planning revision surgery in patients with AKPafter medial patellofemoral ligament reconstruction to detectfemoral tunnel malposition (figure 8).46

In selected cases, such as revision surgery or workers’ com-pensation patients, technetium-99m-methylene diphosphonatescintigraphy may be helpful. It shows the metabolic and geo-graphic characteristics of bone homeostasis.18 A relationship hasbeen demonstrated between an abnormally increased technetiumbone scan of the PFJ and AKP.18 Additionally, an associationbetween restoration to normality of the bone scan and the reso-lution of AKP after conservative treatment has also been docu-mented.18 Näslund et al47 found that nearly 50% of patientswith AKP show a diffuse uptake in the scintigraphy in one ormore of the bony compartments of the knee joint.

Finally, in those cases in which an IMPI is suspected, stressradiography48 or stress axial CT scans49 will be helpful. Theyallow one to objectively document and quantify medial patellarinstability. The difference between the displacement of bothsides carries more importance than the absolute amount of dis-placement (figure 9).

NON-OPERATIVE TREATMENTSince AKP is a multifactorial problem, non-operative manage-ment depends on the examination findings. The clinician needsto decrease the strain of excessively loaded and painful softtissues around the PFJ, improving the seating of the patella inthe trochlea, as well as to optimise the lower limb mechanics,which should decrease the patient’s symptoms and, if main-tained, will minimise any recurrences of symptoms. A multi-modal physiotherapy programme is effective in reducing AKPsymptoms.50 51

Figure 4 Measurement of external tibial rotation using a goniometer and by means of CT. The patient is positioned prone with the knee flexed to90° and the ankle in a neutral position of flexion–extension. (A) Transcondylar axis, (C) longitudinal axis of the femur, and (B) transmalleolar axis.The amount of tibial rotation equals the angle AB.

Figure 5 Lateralisation of the tibial tubercle correlates with anteriorknee pain. When the knee flexes 90°, the patella usually is capturedwithin the trochlea. In an asymptomatic healthy person, the tibialtubercle femoral sulcus angle should be 0° at 90° of knee flexion. Thisangle’s measurement indicates the lateral displacement of the tuberclewith reference to the femoral sulcus.

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Knee pain inhibits quadriceps contraction, decreasing theloading ability of the knee, whereas fear of pain only decreasesvastus medialis oblique (VMO) activity.52 In middle-aged indivi-duals with decreased quadriceps strength, there are reports ofincreased knee pain,53 but MRI scans have also demonstratedincreased patellofemoral cartilage loss and tibiofemoral joint

space narrowing.54 Wang et al55 found that optimising thevastus medialis (VM) size was critical to reducing osteoarthriticprogression and decreasing the need for a total knee replace-ment. Recent evidence of the long-term outcome of treatmentfor adolescents with AKP, who are supposedly compliant with amultimodal exercise programme, is fairly poor, although thesame authors found that the majority of adolescents did notperform the home exercises correctly 2 weeks after their initialinstruction.56 It is hypothesised that the adolescents whosesymptoms fail to improve will develop PFOA.57 Therefore, it isimperative for clinicians to ensure from the beginning that theyget ‘buy in’ with the treatment to ensure compliance, so theclinician must educate the patient about why they have symp-toms, explaining where the pain is coming from, what has con-tributed to the pain and in the first visit significantly reduce thesymptoms.

Explanation to the patientA useful tool for clinicians to give a patient is a modified versionof Dye’s homeostasis of the knee graph, so the patient under-stands the issues of load intensity and load frequency contribut-ing to AKP symptoms (figure 10). The clinician needs to informthe patient about the effect of ADL on knee joint loading, sothe patient understands about keeping inside their envelope offunction to ensure that they are not aggravating their symptomsfurther (box 3).

After the patient has been educated about the effect of loadthrough the knee, the clinician needs to show the patient infront of a mirror his/her lower limb alignment, so the impact ofthe internally rotated femurs and/or pronated feet can be readilyseen. A valuable and easy demonstration to reinforce how prox-imal and distal factors affect the knee is for the clinician to askthe patient to squeeze their gluteals together, causing externalrotation of the femurs and hence a straightening of the knees.The final piece of vital information to improve treatment com-pliance is for the patient to palpate their size of the fat pad onthe symptomatic and asymptomatic sides (the fat pad will belarger in size on the symptomatic side), as well as to feel the dir-ection their patella moves with a quadriceps contraction (thepatella will usually move laterally out of the line of the femur).Appropriate education and understanding helps allay the fear ofpain, which lessens the likelihood of the condition progressingto complex regional pain syndrome (CRPS).

Recognition and treatment of CRPSPatients with AKP, manifesting as CRPS, will demonstrate a tem-perature difference around the knee, with the knee being colder

Figure 6 Functional or dynamic knee valgus visualised by aone-legged squat. It may lead to lateral patellar maltracking. We cansee an internal rotation of the femur secondary to weakness of hipabductors and external rotator muscles. The fact that the patientcannot keep up the hip indicates the weakness of hip abductors. Wecan observe an internal rotation of the tibia secondary to pes pronatus.

Figure 7 Axial MRI. Impingement ofa peripatellar synovitis (arrow).

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than the surrounding tissues, particularly the medial aspect.There may also be a mottling of the skin. It is imperative thatpatients see and feel this so they can understand the effects ofthe sympathetic nervous system. An explanation of the effects ofcentrally maintained pain and a regime of desensitising ishelpful in breaking the pain cycle (figure 11). While there is asignificant temperature difference around the knee, the clinicianshould not touch the patient’s knee or direct specific treatmentto the knee as it will make the symptoms worse.

Unloading painful tissues around the kneeThis involves improving the position of the patella on the femurwith tape and decreasing the stress through any abnormallyloaded structure, which in many cases will be the infrapatellarfat pad (IFP).58 59 Before applying tape, the clinician needs toassess which or all of the following patellar malalignment com-ponents are present to determine how best to improve theseating of the patella in the trochlea for each individual patient:(1) posterior tilt of the inferior pole of the patella into the IFP,which is the most critical component to recognise as taping toolow on the patella can inflame the IFP; (2) lateral tilt of thepatella, indicating tight deep lateral retinacular tissues, whichmay also need to be stretched manually as well as with tape; (3)lateral glide, indicating tight superficial retinacular structures aswell as late onset of VMO contraction and (4) rotation of theinferior pole of the patella such that the long axis of the patelladoes not align with the long axis of the femur.

A symptom producing weight-bearing activity should be usedto determine the effectiveness of the taping, with symptomreduction needing to be at least 50%. In some cases, the fat padmay need to be further unloaded with tape by using two pieces

of tape by lifting the fat pad tissue from the tibial tuberositytowards the patella and anchoring behind the medial and lateralepicondyles, respectively (figure 12). The patient needs to keepthe tape on all the time until the symptoms have subsided,which means they need to be shown how to tape their ownknee, by sitting with the leg out straight on the edge of a chair,so the hamstrings and quadriceps are relaxed and the patella canbe easily moved (figure 13).

Additional control of the patellofemoral alignment may beobtained by rotating the femur externally with tape beginningon the femur and anchoring on the sacrum.

Muscle trainingIn the past, AKP rehabilitation has centred aroundnon-weight-bearing quadriceps activities (straight leg raises andshort arc quadriceps—lifting the lower leg over a rolled towel),which have been shown to be not as effective as glutaeal basedtraining in the short term, promoting rectus femoris rather thanvasti activity and in some situations shown to aggravate thepatient’s symptoms, particularly if the IFP is inflamed.60 Formuscle training to have a lasting effect, it should involve chan-ging the way a patient moves, so PFJ loading can change. Theexercise programme should therefore consist of neuromuscular,weight-bearing training for the whole lower limb, as the femoraland foot positions contribute to altering patellofemoral loadingand weight-bearing promotes balanced quadriceps activation.61

Jensen et al62 showed that 4 weeks of visuomotor skill training,not strength training, improved corticospinal excitability,reinforcing the importance of training specificity, particularlywith regard to gravitational position and force precision.

Figure 8 (A) Three-dimensional CT. Observe a very anterior femoral tunnel used for medial patellofemoral ligament reconstruction (arrow) and (B)a severe patellar chondropathy secondary to this surgical mistake.

Figure 9 Axial stress radiograph ofthe left knee enables us to detect aniatrogenic medial patellar instability.

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Since AKP symptoms are generally increased with loadedknee flexion, clinicians need to retrain the limb position initiallyfor walking. To simulate walking, the patient stands next to thewall with their body turned 45o into the wall, with all theirweight through the leg furthest from the wall and the knee ofthe leg closest to the wall bent onto the wall for balance. Thepatient is instructed to stand tall with the weight back throughthe heel, posteriorly tilt the pelvis and unlock the knee of thestanding leg, while externally rotating the thigh slightly, holdingthe position for 30 s (figure 14A). Degrees of complexity can beadded by using a resistance band tied around the ankle of thenon-weight-bearing leg so the patient can pull the band forwardand back, increasing the resistance for the walking simulation,as well as changing the surface stability using a bosu ball or, ifthe patient wants to practise at home, standing on a pillow(figure 14B).

Daily activity training exercises need to be easily incorporatedinto a patient’s life, so while waiting for the elevator or a bus,the patient can squeeze their glutaeals and slightly bend andthen straighten, not locking, both knees (the first 30o), keepingtheir knees over the middle of their feet. Patients can also prac-tise the walk stance position and flex and extend their kneesslightly, keeping the knees over the second and third toes. Otherdaily strategies involve teaching a patient how to sit and standwithout using their hands to get up and keeping their hips,knees and feet in alignment (avoiding valgus collapse). Sincemany individuals are unaware of their posture when they move,mirrors can be incorporated as useful feedback tools early in therehabilitation programme so that when new activities are added,such as stepping on and off steps and running retraining on a

treadmill, the patient can change their position accordingly,based on evaluating their limb position as seen in the mirror.Simple cues are also effective in changing loading such aslanding with soft knees or landing further towards the toes asthis has been shown to decrease PFJ stress.63 Decreased tibiofe-moral dorsiflexion and subtalar mobility increases the dynamicvalgus collapse seen in many individuals with AKP, so the

Figure 10 Dye’s homeostasis of the knee. To maintain the envelopeof function and remain symptom free the patient must keep theintensity and frequency of the load below the threshold.

Box 3 The patellofemoral joint (PFJ) reaction force andactivities of daily living

▸ 0.5× body weight through PFJ with level walking.▸ 1.5× body weight through PFJ with cycling on a stationary

bike.▸ 3–4× body weight through PFJ with ascending and

descending stairs.▸ 7–8× body weight through PFJ with squatting.▸ 20× body weight through PFJ with jumping.

Figure 11 Desensitising the knee—a variety of different texturedobjects need to be rubbed around the knee by the patient. The objectscould include tissue, cotton wool, sandpaper, ice, etc. This needs to bedone for 5 min every day—30 s to 1 min with each object for about amonth.

Figure 12 Unloading the fat pad—the tape needs to start on thesuperior half of the patella to tilt the inferior pole of the patella out ofthe fat pad, then the fat pad needs to be unloaded by starting at thetibial tubercle with each piece of tape and taping towards the medialand lateral joint lines, forming a wide v shape. The soft tissue is liftedtowards the patella to decrease the tension on the tissues.

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clinician can mobilise to increase the range of the joint/s respon-sible (figure 15).64

The clinician needs to give advice about footwear and ortho-tics. If the navicular drop test is positive (ie, if there is a largedifference between the non-weight-bearing and weight-bearingarch height), then off the shelf foot orthotics are helpful in

minimising patellofemoral symptoms.65 Although some authorshave found that some patients with AKP are that running bare-foot is better for patients with AKP as it decreases PFJ stress, sothey recommend minimalist running shoes with no orthotics, sothere is scope for further investigation identifying different footpostures, categorising responders and non-responders to foot orno foot intervention.

Since muscle tightness can contribute to AKP symptoms,appropriate stretches should be included in the treatmentregimen. The involved muscles may include anterior hip struc-tures, hamstrings, gastrocnemius, rectus femoris as well astensor fasciae latae (TFL)/ITB (figure 16).

Body management strategiesLankhorst et al66 recently found that patients with AKP whohave a delay in initiating treatment and a lower AKP scale at

Figure 13 Self-tape—the patient sits on the edge of a chair with theleg relaxed and extended so it is easy to move the patella. This is aparticularly good way to achieve patella correction as it eliminates theproblem of tight hamstrings causing knee flexion which can be aproblem when the patient tapes the knee in long sitting.

Figure 14 (A) Glutaeal training—the patient stands 45° towards thewall, lifts the knee of the leg closest to the wall onto the wall forbalance. All the patient’s weight is on the standing leg, the weight isback through the heel, the standing knee is slightly flexed, the pelvis isslightly posteriorly tilted. The patient stands tall and very slightlyrotates the standing leg thigh, so the patient feels the glutaealsburning. This exercise is performed frequently throughout the day. Thisis brain training—changing the synergistic activation pattern of thelower extremity muscles for walking and running. (B) This exercise canbe progressed by having the patient stand on a pillow to simulaterough ground.

Figure 15 Mobilisation of the subtalar joint—this is performed inside-lying with the foot maintained at neutral dorsiflexion to simulateheel strike. The clinician everts the calcaneum to increase subtalarpronation immediately after heel strike.

Figure 16 Hamstrings stretch—the patient sits on a kitchen bench orsomewhere so the legs do not touch the ground. The patient sits tall—maintaining a neutral spine, and trunk at 90° to the hips, then thepatient straightens the leg without losing control of the trunk position.This position is held for 15 s and repeated. The leg should not fullyextend, as this will irritate the fat pad—if the clinician is worried aboutthe fat pad being inflamed, then the patient can lean further forwardwhile maintaining a neutral spine which will decrease the load throughthe patellofemoral joint.

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diagnosis are more likely to still have knee pain 6–8 years later,concluding that clinicians need to send patients for appropriatetreatment early. For improved long-term outcome for patientswith AKP, there should be a paradigm shift in the way cliniciansmanage AKP. Since the word exercise conjures up an onerous,time-consuming message to many patients, clinicians need toempower individuals to take charge of their symptoms, empha-sising the need to reinforce appropriate limb alignment withdaily practice, requiring a small amount of time, just like theywould keep their teeth in good health by regular brushing. Toensure the success of the daily strategies and to keep symptomsunder control, the patient would need to visit the clinician every6 months or 12 months for a ‘body maintenance check’, similarto a car service, but for the body, as chronic musculoskeletalconditions are not cured but are managed, so this is one waythat could ensure long-term compliance with a self-managementprogramme.

SURGICAL TREATMENTThe primary treatment for all patients with AKP is non-operative. When non-operative measures fail, and when apatient is in a dysfunctional state requiring intervention, thegoal must be to identify the specific mechanical and/or physicalorigin of the pain before considering any surgery. One shouldalso understand if catastrophising and kinesiophobia are signifi-cant factors before contemplating surgery because psychologicalfactors are pain modulators.20 However, their presence does notcontraindicate surgery if there are objective abnormalities and ifexhaust non-operative measures have failed. The first goal is toidentify whether the pain is articular or extra-articular. The fol-lowing entities may be treated successfully with surgery.

Plica/localised synovial hypertrophyA pathological, painful plica is most readily identified by palpat-ing it in the region in which the patient notes pain, usually inthe medial infrapatellar space. Painful plica may be found inother parts of the knee joint too, so careful palpation aroundthe joint will identify if there is snapping or evidence of atender intra-articular band of tissue which might be causingpain. In such cases, the best treatment is arthroscopic resectionof the painful intra-articular impinging synovial plica structure.Localised synovial hypertrophy around the inferior pole of thepatella and impingement of a peripatellar synovitis (figure 17)could also be successfully treated by means of electrosurgicalsynovectomy.18 67

Retinacular painAs identified by Kasim and Fulkerson,68 any peripatellar retina-cular structure could be a source of AKP. Such pain often goesundiagnosed and is most readily identified by careful palpationof every component around the patella, above and below as wellas medial and lateral to the patella itself, looking for a source oftenderness which reproduces the patient’s pain. Such causes ofpain may be treated effectively by injection of a corticosteroidand/or stretching, but when chronic, retinacular pain is disab-ling, local excision or release may be beneficial and curative.Therefore, identification and surgical extirpation of a chronicsource of retinacular pain are important. Such retinacular painsources may be related to chronic stress as in a chronically tiltedpatella causing pain in the lateral retinaculum. The vastus latera-lis tendon may become constantly irritated in some patients.Pain in the VM tendon, the patellar tendon or the quadricepstendon are treatable by surgical eradication of the chronicallyirritated tissue. Such retinacular pain is sometimes associated

with small nerve injury13 16 and/or substance P production.69

Eradication or transection of the painful small nerves causingthis pain through a localised excision or release is usually suc-cessful.68 One must be particularly careful, however, not tocreate a patella imbalance by release of a painful retinacularstructure that might be also giving important support within theextensor mechanism. This will be particularly true in patientswith trochlear dysplasia and imbalance around the patella. Insuch patients, appropriate treatment of the imbalance and/orcompensatory surgery for the dysplasia may be necessary at thetime of retinacular resection or release. Electrosurgical arthro-scopic patellar denervation could be a good solution for selectedpatients with recalcitrant patellofemoral pain without evidentmechanical anomalies.70

Articular painArticular causes of AKP have been poorly understood. The con-nection between articular lesions of the patella or trochlea andAKP is variable. Many patients with patellofemoral articularlesions have no pain, whereas some people, with cartilage soft-ening only, have excruciating, disabling pain. Therefore, itbehoves the surgeon who is contemplating intervention toassure whether or not a patellofemoral articular lesion is asource of pain. Clinical examination and imaging are essential,along with a detailed history regarding pain triggers. Betweenthe history, observation of the patient doing a single-leg kneebend, and imaging studies to find potential areas of focal over-load, painful lesion localisation should be possible in the major-ity of cases. Fluid signal change on T2-weighted MRIs arediagnostic, as is a positive radionuclide scan. Ho et al71 haveshown fluid signal changes in subchondral bone correlated withoverload. If the imaging studies match the degree of kneeflexion in which pain occurs, one has most likely found anarticular pain source.

Unfortunately, imaging studies do not necessarily identify alesion in all cases. The presence of an objective tilt on axial radi-ography strongly supports focal overload of the lateral PFJ, buta lack of tilt does not rule out focal overload of the distal orlateral patella that may occur functionally in some patients, mostoften female, with delayed centring of the patella in the femoral

Figure 17 Peripatellar synovitis (arrow).

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trochlea in early knee flexion. Such patients may have dysfunc-tion originating at the hip or knee level, or structural trochleadysplasia may lead to focal overload of the distal and/or distal/lateral patella that is held on the lateral trochlea too long inearly knee flexion. Pain in such patients typically occurs on step-ping down with the contralateral leg. Thus, the distal patella ofthe affected side is brought into the focal overload orientationon entry into the trochlea with initial knee flexion. Such pro-blems may be ameliorated by core strengthening, VMOstrengthening and non-operative work including mobilisationthat benefits patellofemoral tracking, but such treatment oftenfails once articular cartilage has begun to deteriorate causingchronic focal subchondral bone irritation. This is first mani-fested as softening or blistering of the overloaded distal/lateralor lateral patella articular cartilage from recurrent focal overloadrelated to structural malalignment and/or functional imbalance(s) of the extensor mechanism.

Some patients may experience painful clicking related to aloose articular fragment in which case an arthroscopic chondro-plasty may provide considerable relief. Microfracture or abrasionarthroplasty has typically been less effective on the patella.

Lateral facetectomy has been helpful in some patients withspecific impingement on the lateral overhanging facet.Unloading of a painful lateral patella articular lesion by antero-medialization (AMZ) of the tibial tuberosity,12 however, pro-vides more profound and prolonged benefit than lateralfacetectomy.

Treatment is best directed at relief of pressure on the area ofpatella focal overload. In patients with an objective patella tiltand a tight lateral retinaculum, lateral release or lengtheningmay be highly effective to unload the lateral, overloaded patellafacet. When the distal patella is more severely involved andchanges extend towards the distal, medial or central aspect ofthe patella, lateral release alone may not be sufficient.Subchondral drilling followed by 6 weeks’ immobilisation works

in some patients, presumably by creating a subchondral ‘healingresponse’ and opportunity for restoration of subchondralhomeostasis.18 In this particular case, we recommend immobil-isation because we are looking for subchondral reconstitution,not cartilage restitution. Bone marrow stimulation by drillingadds the possibility of deep cartilage restoration and subchon-dral remodelling. In patients with AKP and patellar hyperten-sion, extra-articular patellar decompression may offer goodresults.72

AMZ provides more profound unloading of the distal andlateral patella when focal overload related to patella malalign-ment cannot be relieved sufficiently by lateral lengthening orrelease. Once the lateral articular cartilage has collapsed, lateralrelease is less effective and definitive unloading by AMZ may benecessary.73 Pain relief and return to sports are expected afterAMZ for appropriate patients.74 In selected cases, torsional cor-rection surgery should be considered.75

In more extreme cases in which patellofemoral articular painis related to focal or diffuse patellofemoral injury which cannotbe relieved by unloading, articular resurfacing may be war-ranted. A painful medial or trochlear articular lesion may beexcised and resurfaced by an autogenous osteoarticular trans-plant, allograft or biological resurfacing procedure, but resultswith these approaches have been mixed. Osteoarticular allograftresurfacing may be appropriate and can be highly effective inrelieving pain, but carry the risk of late failure.76 Similarly,patellofemoral arthroplasty may become necessary, particularlyin older patients and patients with more diffuse patellofemoraldestruction. In general, most patients with patellofemoral

Box 4 Key issues in patient selection for surgicalprocedures in the treatment of patellofemoral pain

▸ Exhaust all non-operative treatment methods first.▸ Be aware of catastrophising and kinesiophobia and be

particularly sure of objective findings in patients prone tothis condition.

▸ In patients who have already had a patellofemoral surgery,be particularly suspicious of complex instability problemssuch as medial subluxation and neuroma.

▸ Most patients have real pain and one should not assumethat non-operative measures will work in all patients.

▸ Make sure that the patient understands the nature of anyproposed surgery and also be sure that the patient cannotlive with the pain. Modification of activity may be anacceptable alternative to some, particularly older patients.

▸ Design the surgical approach very specifically to target sitesof pain generation.

▸ Be sure to have permission for any potential procedure thatmight be needed at the time of surgery.

▸ Complex regional pain problems should be treated beforesurgical intervention, and surgical intervention should becarefully coordinated with any pain management that isongoing.

Box 5 Tips and tricks in the surgical treatment ofpatellofemoral pain

▸ Use exhaustive physical examination and imaging, andsometimes diagnostic arthroscopy, to accurately define thesite of pain origin.

▸ Use minimalistic approaches whenever possible andappropriate.

▸ Use arthroscopy as a diagnostic tool as well as for treatment.Treatment options may vary depending on specificarthroscopic findings. Don’t perform lateral release for medialsoftening. Lateral release is indicated only for lateralsoftening with patella tilt and a tight lateral retinaculum.

▸ Drilling of articular lesions on the patella should generallybe accompanied by rest and motion with limitedweight-bearing and loading of the joint for about 6 weeks inmost patients.

▸ Unloading of a painful articular lesion on the distal and/orlateral patella by anteromedial tibial tubercle transfer, whenthe patella is overloaded laterally, is a powerful surgicaloption in the treatment of patellofemoral pain resulting fromlateral patella cartilage softening or breakdown.

▸ Lateral retinacular release or lengthening will often giverelief of pain in patients with isolated patella tilt withminimal cartilage breakdown and a tight retinaculum.

▸ Release only what is needed and never release without agood objective reason to do so.

▸ Always encourage early motion without weight-bearing onlyafter tibial tuberosity osteotomy or drilling—one bend a dayis all that is needed.

▸ Maintain quadriceps tone after surgery.

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articular sources of pain, however, can be managed with releas-ing and unloading alternatives.

FUTURE DIRECTIONSThe most challenging patient with AKP in terms of treatment isthe neuropathic patient. Current data suggest that repetitivetranscranial magnetic stimulation of the motor cortex, corre-sponding to the patients’ site of pain, could be a complementarytreatment for patients with chronic neuropathic pain.77 78 Thistreatment could therefore be considered in the subset of patientswith neuropathic pain not responding to more conventionaltreatments. Another emerging promising method in the manage-ment of AKP in patients for whom conservative or surgicaltherapy has failed is radiofrequency neurotomy.79

Finally, we are convinced that the so-called biopsychosocialmodel, currently used in chronic lumbar pain, will soon beapplied in patients with AKP to better understand what is hap-pening in them.80 According to this model, anatomic, biologicaland biomechanical factors must be considered to understandpain, as well as psychological and social factors. Among all thepsychological factors that have been analysed in the patient withAKP, the most relevant one from a clinical standpoint is catastro-phising, which is related to pain as well as to disability.20

Consequently, cognitive behavioural interventions which haveshown the reduction of catastrophising pain in patients with arth-ritis or lumbar pain could also be helpful in patients sufferingfrom AKP.81 82 In this way, we must note that psychological inter-vention in patients who underwent anterior cruciate ligamentreconstruction has shown significant improvements in the short-term clinical results and functional outcomes.83 Catastrophisingrepresents a barrier in the recovery from pain and disability, andtherefore it should be included in the therapeutic targets to com-plement and to improve the results of conventional treatments(such as physical therapy and/or surgery) (boxes 4–6).

Competing interests None declared.

Provenance and peer review Commissioned; externally peer reviewed.

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Box 6 Pitfalls of patellofemoral surgery for pain

▸ Lateral release of a patella that does not have tilt and atight lateral retinaculum may cause medial instability orsubluxation thereby making the patient worse.

▸ Ignoring or missing a symptomatic patella articular lesionwill often yield an unsuccessful surgery, particularly if load isadded to the lesion inadvertently.

▸ A tibial tubercle transfer osteotomy that is not flat, taperedanteriorly at the distal osteotomy, or poorly stabilised willput the patient at risk.

▸ Retinacular causes of pain are often missed and must beidentified and treated to gain optimal pain relief. Sometimesthis requires a local excision of neuromatous or chronicallyirritated tissue.

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Sanchis-Alfonso V, et al. JISAKOS 2016;0:1–13. doi:10.1136/jisakos-2015-000033 13

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Diagnosis and treatment of anterior knee pain

John P FulkersonVicente Sanchis-Alfonso, Jenny McConnell, Joan Carles Monllau and

published online March 22, 2016J ISAKOS 

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